Neocortex (brain): structure and functions

Since the appearance of life on Earth, a great diversity of structures and beings have appeared, evolved and died. Among the various beings who have lived and live on this planet, the animal kingdom to which we belong is one of the most visible, the most interesting and the most debated in the collective imagination.

In most of this area, it is possible to find one of the organs that makes possible our survival and the control of our organism and our behavior: the brain. In this organ the evolution has produced the appearance and the development of several structures, many of them presenting a similar evolution in the majority of the cordados animals.

However, in some species, a structure of great relevance has been developed to explain the ability to organize, think, or have self-awareness, this structure being particularly developed in higher primates and in us humans. This structure is the neoscort or neocortex.

What is the neocortex?

The neocortex, neocortex or isocortex is the structure that in humans makes up most of the cerebral cortex, especially 90% of it. It is the most recent phylogenetic part of the brain. It is mainly composed of gray matter, that is, of somas (the “bodies” of neurons, where the cell nucleus is located) and dendrites of neurons that are part of the brain.

Depending on the area, this structure is between two and four millimeters thick. Despite its small thickness, it is a structure of great extension which by its location inside the skull must be condensed and folded, which is why the human brain has convolutions and curvatures. In fact, although the neocortex takes up roughly the surface of a pizza in its folded state, deployed would occupy two square meters. The human brain is unique in the animal kingdom by its capacity to distribute numerous neuronal sums in a relatively small space.

Thus, the neocortex allows a multitude of neurons to be distributed along several layers of the brain folded on themselves, which in turn has great advantages for our mental performance.

On another side, eThe neocortex is not a uniform structure, but is divided into two cerebral hemispheres.. Additionally, the neocortex shape shapes most of the different brain lobes, affecting the integration and consolidation of virtually all of the information that comes through the senses.

Its functions are therefore multiple and varied, as we will see below.

main duties

Since it constitutes 90% of the cerebral cortex, it is logical to think that this part of the brain is of great importance in the normal functioning of the human being. But what are the functions of this area that make it so important to us?

The neocortex or neocortex is considered to be the area of ​​the brain responsible for our capacity for reasoning, Allow logical thinking and awareness. It is the area of ​​the brain that enables all higher mental functions and executive functions (especially located in the frontal lobe). Self and self-awareness are considered to be due to the functioning of this structure.

It is a set of neurons and glial cells whose function is not to give a stereotypical and predictable response to certain stimuli, but to work on content already processed by other nerve cells to “improvise” original responses in real time.

Reasoning, reflection, decision making …

Also the neocortex it serves as a zone of association and integration of different perceptions and awareness of these, helping to form the most accurate mental picture of reality. It allows for an in-depth analysis of information, thinking and decision-making capacities.

It is the part of the brain that allows planning and anticipation of results, recreating possible scenarios and on this basis allowing the establishment of a strategy or behavior to be followed.

Skills such as arithmetic and language also depend on the neocortex, requiring the integration of different information. and its transformation into different areas of this structure. Likewise, long-term memory also depends largely on the neo-crust, being the zone where new information is “recorded” and from which it is brought back into working memory in order to be able to function with it.

It also enables the development and optimization of other parts of the brain, being able to control behavior, manage emotions and inhibit non-adaptive behaviors, as well as register and consolidate new ones. .

Socially, the neocortex also plays a key role, as it helps to control and manage impulses, emotions and behaviors. This implies that it allows the existence of consideration for others, negotiation of goals and, in general, coexistence with other members of our own species.

Layering organization

In addition to its functional division in the different cerebral lobes and into two hemispheres, it should be noted that the neocortex does not have a homogeneous composition throughout its extent.

In reality, this part of the brain is divided into six distinct layers mainly by the type and organization of the nerve cells found there.

Layer I: outer plexiform layer

Also called the molecular layer, it is the outermost and superficial layer of the neoscort, covered by the piamater (one of the meninges). This first layer contains relatively few neurons. It is responsible for receiving fibers from various brain systems which send information of different types from various parts of the central nervous system.

Its composition is based mainly on horizontal Cajal cells, dendrites of different types of neurons and interneurons and some axons of cells from other more internal layers and structures such as the thalamus. It is a layer that functions as an association layer at the intracortical level, that is, it integrates different types of information creating larger and more meaningful units.

Layer II: Layer of small or granular outer pyramidal cells

This layer of the neocortex is mainly composed of pyramidal and stellate cells (Star shaped), dendrites are located in the outer plexiform layer and axons in the lower layers. Like the previous one, it serves as a mechanism of association between the different parts of the crust, although on another level.

Layer III: outer pyramidal layer

Composed mainly of pyramidal cells of varying size, Although generally higher than that of the outer granular layer. The axons of these form fibers of projection and association. It serves as an intracortical association zone. Also, some of its neurons project contralaterally (towards the other cerebral hemisphere), so that a bridge is established between these two halves of the upper part of the central nervous system.

Coverage IV: Internal granular cover

This layer is mostly made up of star-shaped cells. This layer does not exist in some areas, such as in the motor cortex. It receives information from the thalamus, which is distributed by this layer into what are called the thalamocortical striae. Its fibers project to the basal ganglia, the spinal cord and the brainstem.

Layer V: internal pyramidal or lymph node layer

The fifth layer of the neocortex is made up of large pyramidal cells, With other stars, which send information to other areas of the brain. Within this layer, we observe the Baillarger band, a grouping of nerve fibers located horizontally and which can be distinguished from the adjacent areas that make up the neocortex.

Cover VI: poliform cover

Formed by irregularly shaped and polymorphic cells, this layer of neocortex performs efferent functions, sending connections to white matter and travel many of its neurons through the corpus callosum. In other words, it sends information to relatively remote areas, more than it receives directly from them.

bibliographical references:

  • Hall, J. (2011). Medical physiology textbook by Guyton and Hall. Philadelphia: Saunders / Elsevier.
  • Jerison, HJ (1991). Fossil brains and evolution of the neocortex. At Finlay, BL; Innocenti, G. and Scheich, H. (eds.). The neocortex. Ontogeny and phylogeny. New York: Ed. Plenum Press; p. 5-19.
  • Kandel, ER; Schwartz, JH and Jessell, TM (2001). Principles of neuroscience. Madrid: McGraw Hill.
  • Lewis, WB (1978). On the comparative structure of the cerebral cortex. Brain; 1: 79-86.
  • Morgan, AJ (2001). The evolving brain. Editorial Ariel Neuroscience.

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